The "one inch per gallon" rule

[RighteousRampart19]

Very informative but as in most case with any bigger fish bigger is better?

 

[S0UNDWAV3]

i can only assume my 5 inch female green terror should be ok, she has a 150 litre tank all to her self with homemae caves i built for her, lives better than me haha

 

[kellan]

How much impact do corals and other invertebrate have? Do they help because they capture waste (some at least do), or take up space and make the effective living space less? How about living sand/rock?

 

[Aqua Hero]

This is something that comes up fairly often and is rather misunderstood therefore I will attempt to clarify the original meaning of the general guideline of "one inch of fish per gallon of water".

This is a suggested guideline for a well maintained and filtered tank.
It does not apply to all fish as some have differing requirements.

Here is the part that is being misunderstood.

The "rule" does NOT refer to the length of the fish!

The "rule" applies to the cubic inches of fish in the tank.

This means that a 5" gourami should be measured in this manner,
length overall (5"),
thickness, (1/2"),
height, (2 1/2"),
so for this fish you multiply the following, 5x 1/2x 2 1/2, this gives you a total of 6 1/4 gallons of water.

For small fish like glo-light tetras you will end up with something like this,
1 1/2"x 1/4"x1/2", this comes to 3/16 of a gallon (about 1/5), and that gives you 5 fish of this size per gallon (quite reasonable)

For larger fish you end up with something like this, my example here will be a silver arowana at 24" long, 24"x 4"x 1", which gives you 100 gallons of water.

As you can see this works fairly well.

You do also have to apply some common sense and allow for such things as potential growth, the fish types' tolerance for crowding, and of course the width and length of the tank (a 24" gar will not work in an 18" wide tank even if the tank holds 100 gallons).

So please people, accept that this is just a generalized guideline to figure potential stocking levels, not a hard and fast rule.
Also remember that just because you don't like it doesn't mean you should slam somebody for using it.
And lastly, please don't flame someone by saying a 10" oscar doesn't fit in a 10" tank.
Of course it doesn't,
but the rule never said it would.

the rule is bs to me. its not even a rule

 

[Sergeant Cichlid]

This is something that comes up fairly often and is rather misunderstood therefore I will attempt to clarify the original meaning of the general guideline of "one inch of fish per gallon of water".

This is a suggested guideline for a well maintained and filtered tank.
It does not apply to all fish as some have differing requirements.

Here is the part that is being misunderstood.

The "rule" does NOT refer to the length of the fish!

The "rule" applies to the cubic inches of fish in the tank.

This means that a 5" gourami should be measured in this manner,
length overall (5"),
thickness, (1/2"),
height, (2 1/2"),
so for this fish you multiply the following, 5x 1/2x 2 1/2, this gives you a total of 6 1/4 gallons of water.

For small fish like glo-light tetras you will end up with something like this,
1 1/2"x 1/4"x1/2", this comes to 3/16 of a gallon (about 1/5), and that gives you 5 fish of this size per gallon (quite reasonable)

For larger fish you end up with something like this, my example here will be a silver arowana at 24" long, 24"x 4"x 1", which gives you 100 gallons of water.

As you can see this works fairly well.

You do also have to apply some common sense and allow for such things as potential growth, the fish types' tolerance for crowding, and of course the width and length of the tank (a 24" gar will not work in an 18" wide tank even if the tank holds 100 gallons).

So please people, accept that this is just a generalized guideline to figure potential stocking levels, not a hard and fast rule.
Also remember that just because you don't like it doesn't mean you should slam somebody for using it.
And lastly, please don't flame someone by saying a 10" oscar doesn't fit in a 10" tank.
Of course it doesn't,
but the rule never said it would.

Think its important to not only use your fishes current sizes but take into consideration the size they will grow up to

 

[ShadowP]

"cichlaguapote, post: 1096427, member: 13682"]Very enlightening. I never knew how that works. Through all the flaming always done I thought it was truly supposed to be 1" per gallon not 1 sq" per gallon. Great post.

Cubic Inch... not square... but I always considered the breathing rate of the fish at rest and aimed for about one gill compression every second or slightly longer interval... I once had a 6 gal nano with 1 albino cory, 4 threadfin rainbows, 8 ember tetras, 6 neon tetras, 2 sunset dwarf gourami, and one hillstream loach... all happy with only moderate breathing at rest, and ammonia and nitrites at 0ppm, and nitrates hovering between 10 and 20ppm... about 22" of fish (length only) but far far less cubic inches.

 

[ShadowP]

Anyone else hear of interesting rules for deciding how many fish a tank can comfortably handle?

Yeah, the breathe rate method... it always works.
But I do have a question... lol

I presume you don't count the finnage in the calculations... So
Body only... If I have an Oscar 12" long, and 5" high, and 1.75" thick at the thickest - so let's swag an average thickness overall of 1.2"...
At a total estimated 72 cubic inches of real goldfish eating meat - does this Oscar require 72 gallons of water or 82 gallons of water after eating 5 goldfish at 2" long by 1" high by .5" average thickness? Afterall, don't they say goldfish make a lot of mess?

 

[ShadowP]

Oy!!! Start talking math and everyone goes off on a tangent!

It's 12 square inches of surface area for each inch of fish!!! That would be ONE SQUARE FOOT for a 12" fish... But according to the original post, it would be better stated as per CUBIC INCH OF BODY...
Not the length of the fish squared...
but it's body length times it's body height, times it's average body thickness EQUALS the number of gallons for that fish, NOT COUNTING FOR GROWTH, OR AERATION (surface ripple "doubling factor") etc...
It's a rule of thumb, and so some fish do well and others suffer because our thumbs are all different sizes.

 

[ShadowP]

No because then a 12" oscar would only need an area of 144 sq" which is only one square foot, thats smaller then a ten gallon tank.

Actually a 10 gallon standard tank surface area is 10" x 20" or 200 sq inches.

 

[ShadowP]

Hi again,

The original poster meant 12 square inches

The original poster never even mentioned square inches. The original poster always referenced cubic inches of fish per gallon of water and never mentioned surface area.

Start talking math and everyone goes off on a tangent!!!